content: /*
   * Copyright 2016-present David Karnok
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package hu.akarnokd.rxjava3.parallel;
  
  import org.reactivestreams.*;
  
  import io.reactivex.rxjava3.core.FlowableSubscriber;
  import io.reactivex.rxjava3.internal.subscriptions.*;
  import io.reactivex.rxjava3.parallel.*;
  
  /**
   * Sums numbers as longs on each parallel rail, or empty if the rail doesn't produce any data.
   * @param <T> the input element type extending Number
   * @since 0.16.3
   */
  final class ParallelSumDouble<T extends Number> extends ParallelFlowable<Double> implements ParallelTransformer<T, Double> {
  
      final ParallelFlowable<? extends Number> source;
  
      ParallelSumDouble(ParallelFlowable<? extends Number> source) {
          this.source = source;
      }
  
      @Override
      public ParallelFlowable<Double> apply(ParallelFlowable<T> t) {
          return new ParallelSumDouble<T>(t);
      }
  
      @Override
      public void subscribe(Subscriber<? super Double>[] subscribers) {
          if (!validate(subscribers)) {
              return;
          }
  
          int n = subscribers.length;
          @SuppressWarnings("unchecked")
          Subscriber<Number>[] parents = new Subscriber[n];
          for (int i = 0; i < n; i++) {
              parents[i] = new SumIntSubscriber(subscribers[i]);
          }
  
          source.subscribe(parents);
      }
  
      @Override
      public int parallelism() {
          return source.parallelism();
      }
  
      static final class SumIntSubscriber extends DeferredScalarSubscription<Double>
      implements FlowableSubscriber<Number> {
          private static final long serialVersionUID = -1502296701568087162L;
  
          double sum;
          boolean hasValue;
  
          Subscription upstream;
  
          SumIntSubscriber(Subscriber<? super Double> downstream) {
              super(downstream);
          }
  
          @Override
          public void onNext(Number t) {
              if (!hasValue) {
                  hasValue = true;
              }
              sum += t.doubleValue();
          }
  
          @Override
          public void onError(Throwable t) {
              downstream.onError(t);
          }
  
          @Override
          public void onComplete() {
              if (hasValue) {
                  complete(sum);
              } else {
                  downstream.onComplete();
              }
          }
  
          @Override
          public void onSubscribe(Subscription s) {
              if (SubscriptionHelper.validate(upstream, s)) {
                  upstream = s;
  
                  downstream.onSubscribe(this);
  
                  s.request(Long.MAX_VALUE);
              }
          }
  
          @Override
          public void cancel() {
              super.cancel();
              upstream.cancel();
          }
      }
  
  }
  